Aluminum alloy



alloy shapes.

Patented May 23, 1933 UNITED STATES PATENT, ,OFFICE- FRED.KELLER AND CHARLES M. CRAIGHEAD, OF NEW KENSINGTON, PENNSYLVANIA,

ASSIGNORS TO ALUMINUM COMPANY OF AMERICA, OF PITTSBURGH, PENNSYL- VANIA, A CORPORATION OFTENNSYLVANIA ALUMm'UM ALLOY No Drawing. Original application filed November 30, 1932, Serial No. 645,127. Divided and this application filed February 15, 1933. Serial No. 656,957.

This invention relates to aluminum base alloys which are possessed of high tensile properties, excellent resistance to corrosion, and the further property of retaining a substantial part of their original surface appearance after continued exposure ,to the atmosphere.

There are uses of aluminum base alloys where high strength, good corrosion-resistance and good appearance are primary requisites. Exemplary of such uses are window frames. Such frames are often built up from extruded or rolled aluminum base Since the distinctive color of aluminum lends itself readily to modern design, aluminum base alloys which will retain their natural color and appearance under constant exposure to ordinary or industrial atmospheres are in great demand. The alloys must also, if adaptable to such uses, be of high strength and must likewise be resistant to corrosion in the sense that upon long exposure the tensile properties of' the alloys do not materially depreciate. The known high strength aluminum base alloys have, more or less, fulfilled the above-noted requirements, but there has been a need for an alloy which would combine, to a larger extent, high strength, corrosion-resistance and a stable surface appearance. It is the general'object of this invention to provide alloys of this nature.

Among the high strength aluminum base alloys which are best adapted to the uses and purposes above mentioned are the alloys described in the United States Patent No.

1,472,739 to Robert S. Archer and Zay Jef- I fries. The alloys described in this patent are characterized by the simultaneous presence therein of magnesium and silicon and primarily derive their good tensile properties from the action and effect of these alloying elements under the influence of heattreatment and artificial aging. When magnesium and silicon are together present in aluminum, they form a complex which is usually recognized as the intermetallic compound, Mg si. The compound is to a certainextent soluble in the aluminum. When aluminum containing this compound is thercooled more or less rapidly and thereafter artificially aged by heating to temperatures of about 100 to 200 strength of the alloy is further increased.

In experimenting with this general type of aluminum base alloy we have discovered certain alloys which are generally superior thereto. We have discovered that if an alloy of high tensile properties, excellent corrosion-resistance and stable surface appearance is desired, the best combination of these properties can be obtained when neither an excess of magnesium nor an excess of silicon is present in the alloy, but that the magnesium and silicon should be present in such amounts as will combine substantially completely to form the intermetallic compound Mg Si. Furthermore, as we have discovered,

the alloy should contain from 0.1 to 1.0 perthe aluminum with which they are mixed,

and the other being the fact that in our novel alloys they achieve their stated purpose Without injuring the other desirable properties of the alloy. Likewise they cooperate jointly or severally, as the case may be, to produce the novel composition the properties of' which are herein described. One or more of these metals may be present in the alloy but they should not exceed in total the limits of 0.1 to 1.0 per cent'by weight. When the elements are used singly in the alloy the chromium should not exceed 0.1 to 1.0 per cent by weight, the manganese should not exceed 0.1 to 1.0 per cent by weight, the niolybdenum should not exceed 0.1 to 1.0 per cent by weight, the tungsten should not exceed 0.1 to 0.5 percent by weight, the vanadium should not exceed 0.1

centigrade, the

3.0 per cent by weight of to 1.0 per cent by weight, the zirconium should not'exceed 0.1 to 1.0 per cent by form such amounts of Mg- Si), which contain no substantial excess of magnesiurn'br' silicon over the amounts necessaryto form V Mg Si and which contain 0.1 to 1.0 percent in total of at least one of the elements sten, vanadium, zirconium, titanium, and uranium, the balance of the alloy being aluminum c ontaining not more than 0.3 per cent by weight of impurities exclusive, of course, of silicon, magnesium, chromium, manganese, molybdenum, tungsten, vanadium, zirconium, titanium, and uranium. Al- Toys of this composition. have tensile properties sufficiently high to meet many; engichromium, n manganese, molybdenum, tung-,

named, have, in extruded form and after heat-treatment at, about 515 centigrade followed by cooling and artificial aging at about 160 centigrade for about 18 hours,

an average tensile strength of 35,000 to 39,000 pounds per square inch, an average yield strength of 30,000 to 34,000 pounds per square inch, and an elongationof about 14 to 17 per cent in 2 inches.

- It is further beneficial property ofthe novel alloys herein described'that they are,

under the commercial methods of working and, heat-treatment, singularly free from the phenomena of grain growth or large oru'neven sized grains and that, partlybecause of this fact, they -present in the worked condition a surface which is even and smooth.

This application is .a division of our copending application Serial No. 645,127, filed Nov. 30, I932.

We claim as our invention: An alloy containing about 0.5 to 3.0 per cent by weight of .the intermetallic compound Mg si and about 0.1*to 0.5 per cent by weight of titanium, the balance being aluminum Which does not contain more than 0.3 per cent by weight of impurities exclu- .sive of magnesium, silicon, and titanium.

neering specifications. They have, moreover,

an excellent corrosion-resistance and. stability of surface appearance. In this combination of properties they excel other high In testimony whereof we hereto aifix our signatures. L

FRED KELLER. 4 CHABLESM. CRAIGHEAD.

strength aluminum base alloys known and, v

in addition to these properties, alloys of this composition are readily worked. into usual and even intricate forms and shapes.

The alloys above. described may be heattreated and aged and otherwise thermally treated according to the methods known to the art and may by means of the known methods of working be fabricated into many shapes. The alloys may likewise be cast according to usual foundry practices.

Of the alloys which are the subject of this invention certain are preferred, especially as material from which to form window frames and like articles. These are the alloys'of higher strength which still retain 1 excellent workability. -These alloys contain about 1.5 to 2.0 per cent by'weight ofMg si,

about 0.1 to 1.0 per cent by weight of at least one of the class of elements chromium, manganese, molybdenum, tungsten, vanadium, zirconium, titanium,'and uranium, and the balancebeing aluminum containin not more than about 0.3 per cent by w ight of impurities exclusive of magnesium, silicon, chromium, manganese, molybdenum, tung-; sten, vanadium, zirconium, titanium, and uranium.. For example, alloys containing 1.5 to 2.0 per cent by weight of Mg- Si, 0.1

to 1.5 per cent by weight of chromium, the balance being of the purity above u 

